Impact of thermal properties of veneering ceramics on the fracture load of layered Ce-TZP/A nanocomposite frameworks

ObjectivesThe aim of this in vitro study was to assess the influence of thermal properties of veneering ceramics on the fracture load of layered ceria stabilized zirconia/alumina nanocomposite (Ce-TZP/A) single crowns.MethodsCe-TZP/A single crown frameworks (nanoZr) were veneered with 5 different veneering ceramics for zirconia (Cerabien ZR, IPS e.max, Triceram, Vintage ZR, VM9). In addition, veneering ceramics for alumina (Allux) and for the metal–ceramic technique (Reflex) were included in order to cover a wide range of coefficients of thermal expansion. Fracture load of the crowns was assessed in a shear test (n = 10). Glass transition temperatures (Tg) of the ceramics as well as the coefficients of thermal expansion of the ceramics (αveneer) and Ce-TZP/A (αcore) between 25 and 500 °C were determined (n = 6).ResultsFracture load ranged from 574.0 ± 97.1 N (IPS e.max) to 1009.6 ± 150.0 N (VM9). Δα = αcore − αveneer and ΔT = Tg − 25 °C (ΔT in K) were calculated. The fracture load was strongly correlated to Δα ΔT with a maximum at Δα ΔT ≈ 580 × 10−6.SignificanceThe overall fracture load of veneered Ce-TZP/A crowns is correlated to the thermal properties of the respective veneering ceramic.